This book examines the issue of competing motivations in grammar and language use. The term “competing motivations” refers to the conflicting factors that shape the content and form of grammatical rules and which speakers and addressees need to contend with when expressing themselves, or when trying to comprehend messages. For example, there are on-going competitions between the speaker's interests and the addressee's needs, or between constraints imposed by grammar and those imposed by online processing. These competitions impact a wide variety of systems, including case marking, agreement, and word order, politeness forms, lexical choices, and the position of relative clauses. The twenty-one studies are mostly based on English data but evidence from many languages is also discussed. In addition to grammar and usage in adult language, many of the chapters analyze data from first- and second-language acquisition as well; others probe into the motivations that drive historical change.